This paper [J. Nanophoton. 8(1), 083097 (2014)] was published on 6 January 2014. Thanks to a question by Yoann Brûlé from the Fresnel institute (Marseille, France), we found that the values of γL and γD were swapped in tables in Ref. 1. The problem comes from a bug in the automatic extraction of data from optimization method. Fortunately the curves in Ref. 1 are correct. This erratum gives a more readily available formulation of fitting for all considered metals and the corresponding criteria.
The fitting of metal optical properties is a topic that has applications in advanced simulations of spectroscopy, plasmonics, and optical engineering. In particular, the finite difference time domain method (FDTD) requires an analytical model of dispersion that verifies specific conditions to produce a full spectrum in a single run. Combination of Drude and Lorentz models, and Drude and critical points models, are known to be efficient, but the number of parameters to be adjusted for fitting data can prevent accurate results from simulated annealing or Nelder-Mead. The complex number relative permittivities of Au, Ag, Al, Cr, and Ti from either Palik or Johnson and Christy experimental data in the visible domain of wavelengths are successfully fitted by using the result of the particle swarm optimization method with FDTD constraint, as a starting point for the Nelder-Mead method. The results are well positioned compared to those that can be found in the literature. The results can be used directly for numerical simulations in the visible domain. The method can be applied to other materials, such as dielectrics, and to other domain of wavelengths.
KEYWORDS: Inverse problems, Signal detection, Near field optics, Image processing, Prisms, Data modeling, Chemical elements, Microscopy, Evolutionary algorithms, Near field scanning optical microscopy
In the present work we employ an heuristic method based on evolutionary algorithms for the solution of an inverse problem in near-field optics. The input for the inversion procedure are some of the experimental data that appear in reference 1. In addition, we make use of the direct model proposed in that reference for the iterative solution of the direct problem. This requirement is directly related to the nature of the evolutionary approach employed. We show the possibility to recover, with a high degree of confidence, some parameters of the sample that originated the experimental information. The usefulness of the inverse method is therefore obvious if the recorded data have to be used for metrologic purpose.
A non perturbative Rayleigh method is used to calculate the electromagnetic field in the vicinity of an interface between metal and air. The metallic surface is enlightened by a thin coated nano-source localized a few nanometers above the interface. We study the influence of the size of the tip apparatus and of the distance between the tip end and the sample on the confinements of the spot in the metallic sample. The knowledge of the electromagnetic field in metal could enable to calculate temperature and dilatation of the surface of the metal.
The density of integration of magneto-optical devices is limited by diffraction of light. Recently some groups have proposed to use Near-Field Microscopy to overcome this limitation and some experiments have been performed both in transmission and reflection. In this paper we study theoretically magneto-optical effect in near-field. We consider a magneto-optical sample with details smaller than the wavelength. This sample is modelled as a multilayer rough structure. At least one layer has magneto-optical properties. The corrugation at the interfaces are very small compared to the optical wavelength. We do not consider the writing problem and the experiment is only modelled in the reading mode. Moreover, the magnetic properties are considered in the saturation regime. For this study we use an extension of the method that we used to describe near- field microscope with isotropic sample. The diffracted fields are determined in each layer by using a perturbative version of the Rayleigh method which leads to the resolution of a linear equation for each diffracted wave. The near- field above the sample is thus obtained by summing all the diffracted waves. We consider two geometries for the magnetization: polar effect where the magnetization is perpendicular to the sample and transversal effect where it is in the plane. We compare near-field images obtained in transmission and reflection by changing magnetization orientation. Comparisons with far-field results are also proposed.
KEYWORDS: Near field scanning optical microscopy, Near field optics, Image resolution, Microscopy, Near field, Optical microscopy, Spatial resolution, Optical microscopes, Optical resolution
One of the challenges for newly born probe microscopies is the estimation of their capabilities. The latter is closely related to the reachable resolution. We present a method adapted to these microscopies for determining resolution. It is applied to Reflection Scanning Near-field Optical Microscopy combined with shear-force (ShF) feedback but the method is quite general. The resolution is deduced from the comparison of the optical data spectrum to the shear force data one. Indeed, it is well known that spatial resolution of shear force is better than that of optical microscope and the optical resolution can thus be estimated through this comparison. Actually, the considered set-up uses ShF feedback. Quantitative results are given either with periodic or non periodic objects.
KEYWORDS: Near field scanning optical microscopy, Luminescence, Particles, Chemical species, Interfaces, Modulation, Time metrology, Optical microscopy, Microscopy, Near field optics
We propose a Fluorescent Scanning Near-Field Optical Microscope (FSNOM) based upon the measurement of the decay time of a fluorescent particle adsorbed on a SNOM tip. The purpose of the experiment is to measure the decay time variations of the fluorescent particle when the tip is scanned at a few nanometers from the surface of a sample. We describe the experimental set-up and present a theoretical model: it calculates, by a perturbation method, the variations of the life-time on a rough surface. The formalism is rapidly described and first theoretical life- time signals are presented.
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